Update caused / to become full...

After I updated to ispconfig 2.2 my /dev has become full, thus mysql no longer works etc... What can safely be deleted from /dev/ ? I followed the perfect setup for Ubuntu where they recommende 10 Gb for /dev or root (/)

I was trying to run e2fsck on /dev/hda3 which is full, but when trying to unmount I get the message that the disk is busy? Is it possible to run e2fsck on root, and what can I do to find out what is keeping the disk from being unmounted?

Edit.. Ok appearantly a restart fixed the full /dev... still what can be removed from /dev to ensure enough space?